Fuel tanks on board vehicles of various kinds generally have to meet imperviousness and permeability standards in relation to the type of use for which they are designed and the environmental requirements that they have to satisfy. Both in Europe and throughout the world we are currently experiencing a considerable tightening of the requirements concerned with limiting the emissions of pollutants into the atmosphere and into the environment in general. The design of fuel tanks is therefore evolving quickly towards techniques capable of better guaranteeing the imperviousness and safety under varying conditions of use. Furthermore, attempts are also being made to minimize the losses originating from the pipes and various accessories connected to the tanks. For example, the attaching of pipes and, in particular, of the filler pipe, spouts and flanges to the tank may present problems of permeability. With a view to reducing these problems, various solutions are proposed, most of which call upon an intermediate part or neck. However, problems of imperviousness may still arise at this neck.
Hence, patent application US 2002/0130515 proposes a method for directly incorporating a neck into the tank during the blowing of the latter. However, this solution leads to a neck the wall thickness of which is not constant, something which is not ideal for impervious coupling and, furthermore, may lead to problems of impact strength and additional materials costs (it being necessary to have an excess thickness in order for at least the minimum thickness required to be achieved throughout).
It is therefore an object of the invention to provide a method which also allows a neck to be incorporated into a plastic fuel tank at the time of its manufacture by moulding, but does so using a method and apparatus which are such that the wall thickness of the neck is very uniform and therefore makes it possible to avoid the abovementioned problems.